fix(dkg): relax started atomic ordering from SeqCst to Relaxed#550
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varex83 wants to merge 1 commit into
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fix(dkg): relax started atomic ordering from SeqCst to Relaxed#550varex83 wants to merge 1 commit into
started atomic ordering from SeqCst to Relaxed#550varex83 wants to merge 1 commit into
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The `started` flag in the DKG sync server is a standalone signal that publishes no data of its own: server state lives behind an `RwLock` and wake-ups are delivered via `Notify`. There is only one atomic involved, so the global total order imposed by `SeqCst` is unnecessary; `Relaxed` is sufficient and avoids the extra fences (notably on AArch64). Also document why `Relaxed` is already correct for the QBFT runner's `decided` flag, whose visibility is guaranteed by the spawn_blocking join rather than the atomic ordering.
varex83
changed the title
started atomic ordering from SeqCst to Relaxedstarted atomic ordering from SeqCst to Relaxed
iamquang95
approved these changes
Jul 17, 2026
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Summary
Audited all production atomic-ordering usage in the workspace. The vast majority of sites already use the optimal ordering; this PR addresses the single inefficiency found.
crates/dkg/src/sync/server.rs— thestartedAtomicBoolusedSeqCstfor its store/load (3 sites). The flag is a standalone signal: it publishes no data of its own (server state lives behind theRwLock, wake-ups come fromNotify), and it is the only atomic in play. A global total order (SeqCst) is therefore unnecessary — it just adds fences (dmb ish+ldar/stlron AArch64;xchg/mfencevs. plainmovon x86). Downgraded toRelaxed, which is sufficient for the register-then-checkNotifyidiom (correctness comes from registeringnotified()before the load, not from the atomic's ordering).Also added an explanatory comment on the QBFT runner's
decidedflag documenting why its existingRelaxedload is already correct (visibility is guaranteed by thespawn_blockingjoin, not the atomic ordering).Audit result (production sites)
consensus/instance.rsRelaxedMutex)consensus/qbft/p2p.rs,parsigex/behaviour.rsRelaxedconsensus/qbft/runner.rsdecidedRelaxeddkg/sync/server.rsstartedSeqCst→RelaxedNo correctness bugs were found — no
Relaxedsite was dangerously under-strengthened.Testing
cargo build -p pluto-dkg -p pluto-consensuscargo clippy -p pluto-dkg -p pluto-consensus --all-targets --all-features -- -D warnings